Perpendicular magnetic recording media, manufacturing process of the same, and magnetic storage apparatus using the same

ABSTRACT

Provided are a double-layer perpendicular magnetic recording medium having a high medium S/N at an areal recording density of 50 Gbits or more per square inch, and a magnetic storage apparatus having excellent reliability with a low error rate. The perpendicular magnetic recording medium is formed by sequentially laminating a domain control layer, an amorphous soft magnetic underlayer, an intermediate layer, and a perpendicular recording layer on a substrate. The domain control layer is a triple-layer film formed by laminating a first polycrystalline soft magnetic layer, a disordered antiferromagnetic layer, and a second polycrystalline soft magnetic layer from a substrate side.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a magnetic recording medium anda magnetic storage apparatus, specifically to a magnetic recordingmedium having a recording density of 50 Gbits or more per square inchand to a magnetic storage apparatus incorporating the same.

[0002] In recent years, an areal recording density of a magnetic diskdevice as an external storage apparatus of a computer is increased by100% per year. However, as the areal recording density is increased, aproblem that data magnetically recorded is erased by circumferentialheat, that is, a so-called thermal fluctuation, has become obvious.Accordingly, the conventional longitudinal recording method has beenconsidered to be difficult to achieve the areal recording densityexceeding 50 Gbits per square inch.

[0003] On the other hand, unlike the longitudinal recording method, aperpendicular recording method has a feature that, as a linear recordingdensity is increased, a demagnetizing field acting between adjacent bitsis decreased to stabilize recorded magnetization. Accordingly, theperpendicular recording method is considered to be one of the effectivemeans for exceeding the thermal fluctuation limit of the longitudinalrecording method.

[0004] In the perpendicular recording method, a combination of a singlepole type head and a double-layer perpendicular medium composed of asoft magnetic underlayer and a perpendicular recording layer iseffective in realizing high density recording. However, since thedouble-layer perpendicular medium includes the soft magnetic underlayerof a high saturation magnetic flux density (Bs), following problems havebeen pointed out: a stray field generated from domain walls of the softmagnetic underlayer is observed as spike noises, or recordedmagnetization disappears by displacement of domain walls of the softmagnetic underlayer. As a method for solving these problems, for exampleas disclosed in Japanese Patent Laid-Open Nos. 07(1995)-129946 and11(1999)-191217, it has been proposed that a hard magnetic pinning layeris provided between the soft magnetic layer and a substrate so thatmagnetization directions of the soft magnetic layer are aligned with onedirection. As disclosed in Japanese Patent Laid-Open No.06(1994)-103553, a method has been proposed, in which the displacementof domain walls of the soft magnetic layer is suppressed by an exchangecoupling with an antiferromagnetic layer having magnetic spins alignedwith each other.

[0005] However, in the method of aligning magnetization directions ofthe soft magnetic underlayer by use of the hard magnetic pinning layer,magnetic domains having an opposite magnetization direction are likelyto be formed around inner and outer edges a disk substrate, and spikenoises therefrom are observed. On the other hand, the method ofsuppressing the displacement of domain walls of the soft magneticunderlayer by use of the antiferromagnetic layer has an effect forpreventing the disappearance of the recorded magnetization, which iscaused by the displacement of domain walls, but cannot prevent the spikenoises attributable to the domain walls.

SUMMARY OF THE INVENTION

[0006] The present invention is made to solve the above problems.Specifically, an object of the present invention is to provide aperpendicular magnetic recording medium having a recording density of 50Gbits or more per square inch and a high medium SIN, which suppressesspike noises from the soft magnetic underlayer by a magnetic domaincontrol layer and to provide a manufacturing process of the same, so asto facilitate realization of a high-density magnetic storage apparatus.

[0007] In the perpendicular magnetic recording medium including a domaincontrol layer, an amorphous soft magnetic underlayer, and aperpendicular recording layer, which are sequentially formed on asubstrate, the domain control layer is a triple-layer film including afirst polycrystalline soft magnetic layer, a disorderedantiferromagnetic layer, and a second polycrystalline soft magneticlayer, which are sequentially formed from a substrate side, so thatdomain control of the soft magnetic underlayer and reduction of mediumnoises can be achieved.

[0008] The inventors found out that the domain control layer as theabove triple-layer film was effective as a result of investigation ofvarious kinds of method for the domain control of the amorphous softmagnetic underlayer. Each of the first and the second polycrystallinesoft magnetic layers is required to be capable of offering a softmagnetic property at a small film thickness and to have a good latticematching with the disordered antiferromagnetic layer. Specifically, forthe first and the second polycrystalline soft magnetic layers, aface-centered cubic (fcc) alloy mainly composed of Ni and Fe or an fccalloy mainly composed of Co can be employed. Examples of these alloysinclude a Ni₈₁Fe₁₉ alloy, a Ni₈₀Fe20 alloy, Co, and a Co₉₀Fe₁₀ alloy.Here, a numeral following a symbol of an element means a content of theelement in atomic percent.

[0009] At formation of the disordered antiferromagnetic layer, aninterlayer exchange coupling is necessary to act between the disorderedantiferromagnetic layer and the first polycrystalline soft magneticlayer. Specifically, for the disordered antiferromagnetic layer, adisordered alloy mainly composed of Mn and Ir, or a disordered alloymainly composed of Cr, Mn, and Pt can be employed. When the domaincontrol layer is formed using such a material while applying a magneticfield having a component of a parallel direction to a surface of thesubstrate, a unidirectional magnetic anisotropy is induced in adirection of applying the magnetic field, so that the magnetizationdirections of the first and the second polycrystalline soft magneticlayer can be aligned with the direction of the applied magnetic field.Specifically, when the domain control layer using the above material isformed by a magnetron sputtering method, the magnetization directions ofthe first and the second polycrystalline soft magnetic layers can bealigned with a direction of a stray field from a cathode, that is, aradial direction of the disk substrate. As described above, the spikenoises can be effectively suppressed by providing the domain controllayer with a unidirectional magnetic anisotropy. On the other hand,since the ordered antiferromagnetic alloy such as a PtMn alloy and aNiMn alloy is generally in a disordered state at film formation, theexchange coupling does not act between the antiferromagnetic layer usingsuch materials and the first polycrystalline soft magnetic layer.Accordingly, after the film formation, an ordering heat treatment isrequired for several hours while applying a magnetic field. Such a stepis not desirable because a medium manufacturing process is madecomplicated and then costs are increased.

[0010] In the case of using the magnetron sputtering apparatus, theamorphous soft magnetic underlayer is provided with a uniaxial magneticanisotropy having an easy axis of magnetization along the radialdirection of the disk substrate during the medium manufacturing process.In the case where the domain control layer is not provided, severalspoke-like 180° domain walls exist on the disk substrate so as to lowermagnetostatic energy. By using the domain control layer of the presentinvention, the exchange coupling acts between the second polycrystallinesoft magnetic layer and the amorphous soft magnetic underlayer, so thatthe amorphous soft magnetic underlayer is provided with theunidirectional magnetic anisotropy having the easy direction ofmagnetization aligned with the magnetization direction of the secondpolycrystalline soft magnetic layer. Accordingly, the spoke-like domainwalls can be removed except the inner and outer edges of the disksubstrate. Since magnetic poles are formed at the edges of the disksubstrate, magnetic domains are formed so as to lower magnetostaticenergy. However, in the medium of the present invention, an area havingthe magnetic domains formed thereon can be suppressed within areas of 1mm from the edges of the disk substrate, that is, areas other than adata area. As a film thickness of the amorphous soft magnetic underlayeris increased, the exchange coupling force from the domain control layeris relatively decreased, so that the domain formation area around theedges of the disk substrate is expanded. In such a case, the amorphoussoft magnetic underlayer is divided into two layers, and the domaincontrol layer is inserted therebetween, thus reducing the domainformation area around the edges of the disk substrate. A material of theamorphous soft magnetic underlayer is not particularly limited, as longas the material is an amorphous alloy having Bs at least not less than 1tesla (T), having an excellent surface flatness, and not crystallizingin the medium manufacturing process. Specifically, an amorphous alloy,which is mainly composed of Fe or Co and to which Ta, Hf, Nb, Zr, Si, B,or the like are added, can be employed.

[0011] For the intermediate layer used in the perpendicular recordingmedium of the present invention, a nonmagnetic alloy, which is amorphousor has a hexagonal closed packed (hcp) structure, can be employed. Forthe perpendicular recording layer, a CoCrPt alloy, a Co/Pd multilayerfilm, a Co/Pt multilayer film, or the like can be employed. Inparticular, since each of the Co/Pd multilayer film and the Co/Ptmultilayer film of a small thickness offers a high coercivity not lessthan 5 kOe, resolution can be improved.

[0012] As for a protective layer of the perpendicular recording layer, afilm mainly composed of carbon is formed with a film thickness rangingfrom 3 nm to 10 nm, and a lubricating layer is further formed ofperfluoroalkylpolyether or the like at a film thickness ranging from 1nm to 10 nm, whereby the perpendicular magnetic recording medium, whichhas an excellent reliability, can be obtained.

[0013] A magnetic storage apparatus of the present invention includesthe above-described perpendicular magnetic recording medium; a drivingunit for driving the perpendicular magnetic recording medium in arecording direction; a magnetic head composed of a recording section anda reproducing section; a unit for relatively moving the magnetic headwith respect to the perpendicular recording medium; and a recording andreproducing processing unit for inputting signals to the magnetic headand for reproducing output signals from the magnetic head. Thereproducing section of the magnetic head is composed of a highsensitivity element utilizing a magnetoresistive effect or a tunnelingmagnetoresistive effect. Accordingly, the magnetic storage apparatus canbe realized, which has an excellent reliability at the recording densityof 50 Gbits or more per square inch.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a view showing a layer structure of a perpendicularmagnetic recording medium of an embodiment of the present invention.

[0015]FIG. 2 is a view showing a layer structure of a domain controllayer.

[0016]FIG. 3 is a view showing a layer structure of a perpendicularmagnetic recording medium of a comparison.

[0017]FIGS. 4A to 4C are views showing magnetization curves of anamorphous soft magnetic underlayer.

[0018]FIG. 5A is a view showing a relationship between an exchange biasfield and a film thickness of an MnIr layer; and FIG. 5B is a viewshowing a relationship between a coercivity and the film thickness ofthe MnIr layer.

[0019]FIG. 6A is a view showing a relationship between an exchange biasfield and a film thickness of a CrMnPt layer; and FIG. 6B is a viewshowing a relationship between a coercivity and the film thickness ofthe CrMnPt layer.

[0020]FIG. 7 is a cross-sectional TEM image of a section of the domaincontrol layer and the amorphous soft magnetic underlayer.

[0021]FIG. 8 is a view showing X-ray diffraction patterns of theperpendicular magnetic recording media.

[0022]FIG. 9 is a view showing a layer structure of a perpendicularmagnetic recording medium of an embodiment of the present invention.

[0023]FIG. 10 is a schematic sectional view of a head which has a readelement and a write element.

[0024]FIG. 11A is a schematic plan view of a magnetic storage apparatusof an embodiment of the present invention; FIG. 11B is a longitudinalsectional view taken along a line A-A′ of FIG. 11A.

[0025]FIG. 12 is a view showing a layer structure of a high sensitivityelement utilizing a tunneling magnetoresistive effect.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Next, description will be made for embodiments with reference tothe accompanying drawings.

[0027] [Embodiment 1]

[0028]FIG. 1 shows a layer structure of a perpendicular recording mediumof the embodiment. A 2.5-inch glass disk subjected to alkaline cleaningwas employed as a substrate 11. On the substrate 11, sequentiallydeposited were a domain control layer 12, an amorphous soft magneticunderlayer 13, an intermediate layer 14, a perpendicular recording layer15, and a protective layer 16 by a DC magnetron sputtering method. Asshown in FIG. 2, the domain control layer 12 was a triple-layer filmconstituted of a first polycrystalline soft magnetic layer 21, adisordered antiferromagnetic layer 22, and a second polycrystalline softmagnetic layer 23. A target used for the preparation of each of thelayers and a film thickness thereof are shown in Table 1. For thedisordered antiferromagnetic layer, a MnIr alloy or a CrMnPt alloy wasemployed. TABLE 1 Target Film composition thickness (at %) (nm) Firstpolycrystalline soft magnetic layer Ni₈₁Fe₁₉ 5 Disorderedantiferromagnetic layer Mn₈₀Ir₂₀ 2-50 Cr₄₈Mn₄₈Pt₄ 15-50 Secondpolycrystalline soft magnetic layer Ni₈₁Fe₁₉ 5 Amorphous soft magneticunderlayer Co₉₂Ta₃Zr₅  50-200 Intermediate layer Ni_(52.5)Ta_(37.5)Zr₁₀5 Perpendicular recording layer Co₆₄Cr₂₂Pt₁₄ 20 Protective layer Carbon5

[0029] The amorphous soft magnetic underlayer 12 was formed under aprocess condition in film preparation that Ar gas pressure was 0.5 Pa,and then the substrate was heated by a lamp heater. At the formation ofthe intermediate layer 14, a substrate temperature was about 250° C. Thelubricating layer 17 was formed by coating a perfluoroalkylpolyethertype material diluted with a fluorocarbon material. As a comparison, amedium without the domain control layer, as shown in FIG. 3, wasprepared under the same process conditions in film preparation as thosein the embodiment.

[0030] In order to evaluate magnetic properties of the amorphous softmagnetic underlayer of the embodiment, magnetization curves weremeasured by using a vibrating sample magnetometer (VSM), where a sampleof 8 mm square cut out from the disk substrate was used. An examplethereof is shown in FIGS. 4A to 4C. The magnetization curve (FIG. 4A)measured by applying a magnetic field along the radial direction of thedisk substrate has a narrow range of the applied field for magnetizationreversal, and a shift of the magnetization curve is seen along thedirection of the magnetic field. Here, the magnetic field and themagnetization from the inner circumference toward the outercircumference in the radial direction of the disk substrate are shown aspositive values. By magnifying a circle portion of FIG. 4A, hysteresisis seen (FIG. 4B), and the portion corresponds to a magnetization curveof the first polycrystalline soft magnetic layer of the domain controllayer. On the other hand, in the magnetization curve (FIG. 4C) measuredby applying a magnetic field along the circumferential direction of thedisk substrate, the magnetization is substantially linearly changed, anda shift of the magnetization curve is not seen along the direction ofthe magnetic field. These results reveal that the amorphous softmagnetic underlayer of the present invention is provided with a uniaxialmagnetic anisotropy having an easy axis of magnetization along theradial direction of the disk substrate, and further provided with aunidirectional magnetic anisotropy having an easy direction ofmagnetization in a radial direction from the outer circumference towardthe inner circumference.

[0031] Next, in order to examine a magnetic property distribution of theamorphous soft magnetic underlayer (film thickness: 50 nm) with respectto locations on the disk substrate, B-H curves were measured at 16locations on the same circumference of the disk substrate by using a B-Htracer. Here, a magnetic field was applied along a radial direction ofthe disk substrate. In Table 2, exchange bias fields Hex andcoercivities Hc of the amorphous soft magnetic underlayer are shown.Here, Hex is a shift amount of the B-H curve along the direction of themagnetic field. TABLE 2 Location on disk substrate Angle (deg) Hex (Oe)Hc (Oe) 1 0 19.7 2.6 2 22.5 20.1 2.4 3 45.0 20.3 2.3 4 67.5 20.3 2.5 590.0 20.6 2.3 6 112.5 20.2 2.2 7 135.0 20.4 2.4 8 157.5 20.2 2.6 9 180.020.1 2.3 10 202.5 20.1 2.5 11 225.0 20.3 2.3 12 247.5 19.9 2.1 13 270.019.9 2.3 14 292.5 20.1 2.6 15 315.0 20.3 2.4 16 337.5 20.1 2.3

[0032] Hex and Hc are changed a little depending on the measurementlocations. In each of the B-H loops, the zero field axis was on theoutside (the left side) of the portion having the hysteresis. In otherwords, the residual magnetization of the amorphous soft magneticunderlayer is considered to be substantially aligned in a radialdirection from the outer circumference toward the inner circumferencewithout depending on the locations in the disk substrate. Actually, whenobservation of the magnetic domains was carried out by a Bitter method,no clear domain walls could be observed in the disk substrate other thanthe edges thereof. It was confirmed that areas of the magnetic domainsformed around the inner and outer edges of the disk were restrictedwithin 1 mm from the disk edges.

[0033] Next, effects of the film thickness of the disorderedantiferromagnetic layer on magnetic properties of the amorphous softmagnetic underlayer (film thickness: 50 nm) were examined in such amanner that B-H curves were measured by applying a magnetic field alonga radial direction, and the exchange bias field Hex and the coercivityHc were evaluated. As shown in FIGS. 5A and 5B, in the case of using anMnIr alloy for the disordered antiferromagnetic layer, a large Hex canbe obtained with a film thickness thereof as thin as 5 nm, and Hex isdecreased with an increase in film thickness to be substantiallyconstant with a film thickness of 15 nm or more. Hc is considerablyincreased in the case of a film thickness of 2 nm, but is decreased tobe sufficiently lower than Hex with a film thickness of 5 nm or more. Onthe other hand, as shown in FIGS. 6A and 6B, in the case of using aCrMnPt alloy for the disordered antiferromagnetic layer, themagnetization curve is shifted with a film thickness of 30 nm or more,and then Hc is decreased in accordance with the shift of themagnetization curve. From these results, it is considered that, in orderto control the magnetic domains of the amorphous soft magneticunderlayer, the disordered antiferromagnetic layer is required to have afilm thickness of at least about 5 nm in the case of the MnIr alloy orat least about 30 nm in the case of the CrMnPt alloy.

[0034]FIG. 7 shows a transmission electron microscopy (TEM) image of thedomain control layer and the amorphous soft magnetic underlayer in thecase of using the CrMnPt alloy for the disordered antiferromagneticlayer. On the surface of the domain control layer, roughness of about 3nm is seen, but the surface of the amorphous soft magnetic underlayer iscomparatively flat, which comes from the fact that the soft magneticunderlayer is amorphous. Since the surface flatness of the soft magneticunderlayer gives an effect on crystal orientation of the perpendicularrecording layer formed on the soft magnetic underlayer via theintermediate layer, the surface of the soft magnetic underlayer isdesirably as flat as possible.

[0035]FIG. 8 shows X-ray diffraction results of the media of theembodiment and the medium of the comparison without the domain controllayer. Regarding the two patterns of the embodiments in FIG. 8, theupper pattern is an X-ray diffraction pattern of the medium using theCrMnPt alloy for the disordered antiferromagnetic layer, and the lowerpattern is an X-ray diffraction pattern of the medium using the MnIralloy for the disordered antiferromagnetic layer. Δθ₅₀ of the embodimentobtained by rocking curves of CoCrPt (00.2) diffraction peaks, whichprovides an indication to c⁻axis vertical orientation of theperpendicular recording layer, are a little larger than that of themedium of the comparison. Accordingly, it is found that deterioration ofthe crystal orientation of the perpendicular recording layer byinsertion of the domain control layer is small.

[0036] Next, spike noises in the media of the embodiment using the MnIralloy for the disordered antiferromagnetic layer and in the media of thecomparison are evaluated by use of a spin stand. The media of theembodiment including the soft magnetic underlayers (CO₉₂Ta₃Zr₅) havingdifferent film thicknesses of 50 nm, 100 nm, and 200 nm were prepared asmedia A, B, and C, respectively, and the media of the comparisonincluding the soft magnetic underlayers (CO₉₂Ta₃Zr₅) having differentfilm thicknesses of 50 nm, 100 nm, and 200 nm were prepared as media D,E, and F, respectively. In Table 3, the exchange bias field Hex and thecoercivity Hc of the amorphous soft magnetic underlayer, and the numberof spike noises per one round of the disk are shown for each medium.TABLE 3 Film thickness of soft magnetic underlayer Hex Hc Number ofspike (nm) (Oe) (Oe) noises Embodiment 1 Medium A 50 20.6 2.3 NoneMedium B 100 9.8 1.9 None Medium C 200 5.1 0.8 1 Medium D 50 0 1.7 Notless than 20 Comparison Medium E 100 0 1.6 Not less than 20 Medium F 2000 0.6 6

[0037] In the media of the comparison without the domain control layer,a lot of large spike noises were observed in one round of the disk. Whenthe radial location for the observation was changed, the spike noiseswere observed at the substantially same circumferential locations.Accordingly, it is found that spoke-like 180° domain walls exist in thedisk. On the other hand, in the media of the embodiment with the domaincontrol layers, one spike noise was observed in the innercircumferential portion only in the case where the amorphous softmagnetic underlayer had a thickness of 200 nm. However, in the case ofthe amorphous soft magnetic underlayers having thicknesses of 100 nm and50 nm, no spike noises were observed over the entire surface of thedisk. Therefore, by using the domain control layer of the presentinvention, the magnetic domains of the amorphous soft magneticunderlayer can be allowed to be a quasi- single magnetic domain duringthe medium forming process, thus making it possible to considerablysuppress the spike noises.

[0038] [Embodiment 2]

[0039]FIG. 9 shows a layer structure of a perpendicular recording mediumof the embodiment. A 2.5-inch glass substrate 11 subjected to alkalinecleaning was employed as the substrate 11. On the substrate 11,sequentially deposited were a domain control layer 91, an amorphous softmagnetic underlayer 92, a domain control layer 93, an amorphous softmagnetic underlayer 94, the intermediate layer 14, the perpendicularrecording layer 15, and the protective layer 16 by the DC magnetronsputtering method. Each of the domain control layers 91 and 93 was atriple-layer film constituted of the first polycrystalline soft magneticlayer 21, the disordered antiferromagnetic layer 22, and the secondpolycrystalline soft magnetic layer 23 as shown in FIG. 2. A target usedfor the preparation of each of the layers and a thickness thereof areshown in Table 4. The amorphous soft magnetic underlayer 12 was formedunder a process condition in film preparation that Ar gas pressure was0.5 Pa, and then the substrate was heated by a lamp heater. During theformation of the intermediate layer 14, a substrate temperature wasabout 250° C. The lubricating layer 17 was formed by coating aperfluoroalkylpolyether type material diluted with a fluorocarbonmaterial. TABLE 4 Target Film composition thickness (at %) (nm) Firstpolycrystalline soft magnetic layer Ni₈₁Fe₁₉ 5 Co₉₀Fe₁₀ 10 Disorderedantiferromagnetic layer Mn₈₀Ir₂₀ 10 Second polycrystalline soft magneticlayer Ni₈₁Fe₁₉ 5 Co₉₀Fe₁₀ 5 Amorphous soft magnetic underlayerCo₉₂Ta₃Zr₅ 100/100 Intermediate layer Ni_(52.5)Ta_(37.5)Zr₁₀ 5Perpendicular recording layer Co₆₄Cr₂₂Pt₁₄ 20 Protective layer Carbon 5

[0040] Magnetic properties of the amorphous soft magnetic underlayer ofthe embodiment were evaluated by use of the B-H tracer. In Table 5, theexchange bias field Hex and the coercivity Hc were shown in each case ofusing Ni₈₁Fe₁₉ (medium G) and using Co₉₀Fe₁₀ (medium H) for the firstand the second polycrystalline soft magnetic layers. TABLE 5 First andsecond polycrystalline soft magnetic Hex Hc Number of layers (Oe) (Oe)spike noises Embodiment 2 Medium G Ni₈₁Fe₁₉ 12.5 0.7 None Medium HCo₉₀Fe₁₀ 16.4 0.8 None

[0041] When the two amorphous soft magnetic underlayers were provided byinterposing the domain control layer therebetween, Hex two times or moreof and Hc equivalent to those in the case of using the single amorphoussoft magnetic underlayer (Embodiment 1: medium C) were obtained. In theevaluation of the spike noises of the media of the embodiment by use ofthe spin stand, no spike noise was observed over the entire surface ofthe disk.

[0042] Recording and reproducing were carried out under the conditionthat a head flying height is 10 nm by use of the medium G of theembodiment, a single pole type head having a track width of 0.25 μm forrecording, and a GMR head having a track width of 0.22 μm and a shieldgap of 0.08 μm for reproducing. When a reproduced waveform of signalswas passed through an EEPR4 series signal processing circuit for anerror rate evaluation of the signals, an error rate of 10³¹ ⁶ or lesswas obtained under the condition that the areal recording density was 50Gb/in². Note that a head which has a read element and a write elementused in the evaluation has a known constitution composed of a main pole101, a recording coil 102, an auxiliary pole/upper shield 103, a GMRelement 104, and a lower shield 105 as shown in FIG. 10.

[0043] [Embodiment 3]

[0044] Description will be made for a magnetic storage apparatusaccording to the present invention with reference to FIGS. 11A and 11B.FIG. 11A is a schematic plan view of the apparatus, and FIG. 11B is asectional view taken along a line A-A′ of FIG. 11A. The magnetic storageapparatus has a known constitution composed of a perpendicular magneticrecording medium 111; a driving section 112 for rotationally driving theperpendicular magnetic recording medium 111; a magnetic head 113; adriving unit 114 for driving the magnetic head 113; and arecording/reproducing signal processing unit 115 forinputting/reproducing signals into/from the magnetic head 113. Themagnetic head 113 is a head which has a read element and a write elementformed on a magnetic head slider. The single pole type recording headhas a track width of 0.25 μm, and the GMR head for reproducing has ashield gap of 0.08 μm and a track width of 0.22 μm.

[0045] A recording/reproducing property was evaluated by incorporatingthe medium G of the embodiment 2 into the above magnetic storageapparatus under the following conditions: a head flying height of 10 nm;a linear recording density of 590 kBPI; and a track density of 89 kTPI.The magnetic storage apparatus fully satisfied a recording/reproducingproperty specification at an areal recording density of 52.5 Gb/in² in atemperature range from 10° C. to 50° C.

[0046] [Embodiment 4]

[0047] The medium H of the embodiment 2 was incorporated in a magneticstorage apparatus using a high sensitivity element utilizing a tunnelingmagnetoresistive effect, which has a similar constitution to themagnetic storage apparatus of the embodiment 3. Therecording/reproducing property was evaluated under the followingconditions: a head flying height of 10 nm; a linear recording density of674 kBPI; and a track density of 89 kTPI. The magnetic storage apparatusfully satisfied a recording/reproducing property specification at anareal recording density of 60 Gb/in² in a temperature range from 10° C.to 50° C. Specifically, the high sensitivity element utilizing atunneling magnetoresistive effect, which was used in the evaluation, hasa known constitution composed of an upper electrode 121, anantiferromagnetic layer 122, a pinned layer 123, an insulating layer124, a free layer 125, and a lower electrode 126.

[0048] A manufacturing process of a perpendicular magnetic recordingmedium according to the present invention comprises the steps of:forming a disordered antiferromagnetic layer on a substrate; forming apolycrystalline soft magnetic layer on the antiferromagnetic layer; andforming an amorphous soft magnetic layer on the polycrystalline softmagnetic layer; wherein said every steps are carried out while applyinga magnetic field having a component parallel to a surface of thesubstrate. A direction of the magnetic field having a component parallelto the surface of the substrate is substantially parallel to a radialdirection of the substrate.

[0049] The magnetic storage apparatus according to the present inventioncomprises: a perpendicular magnetic recording medium mentioned above; adriving section for driving the perpendicular magnetic recording mediumin a recording direction; a magnetic head including a reproducingsection and a recording section; a unit for relatively moving themagnetic head with respect to the perpendicular magnetic recordingmedium; and a recording and reproducing processing unit for inputtingsignals into said magnetic head and for reproducing output signals fromthe magnetic head, wherein said reproducing section of the magnetic headis composed of a high sensitivity element utilizing a magnetoresistiveeffect or a tunneling magnetoresistive effect, and said recordingsection of the magnetic head is composed of a single pole type head.

[0050] According to the present invention, the magnetic storageapparatus can be realized, which has an excellent reliability with a lowerror rate at an areal recording density of 50 Gbits or more per squareinch.

What is claimed is:
 1. A perpendicular magnetic recording medium, comprising: a substrate; a perpendicular recording layer; an antiferromagnetic layer formed between said substrate and said perpendicular recording layer; an amorphous soft magnetic layer formed between said antiferromagnetic layer and said perpendicular recording layer; and a crystalline soft magnetic layer formed adjacent to said amorphous soft magnetic layer on a substrate side thereof.
 2. A perpendicular magnetic recording medium, comprising: a domain control layer including an antiferromagnetic layer and a crystalline soft magnetic layer formed on said antiferromagnetic layer; an amorphous soft magnetic layer formed on said domain control layer; and a perpendicular recording layer formed on said amorphous soft magnetic layer directly or via an intermediate layer, wherein said crystalline soft magnetic layer is formed adjacent to said amorphous soft magnetic layer.
 3. The perpendicular magnetic recording medium according to claim 1, further comprising: a crystalline soft magnetic layer formed between said substrate and said antiferromagnetic layer.
 4. The perpendicular magnetic recording medium according to claim 1, further comprising: an intermediate layer formed between said amorphous soft magnetic layer and said perpendicular recording layer.
 5. The perpendicular magnetic recording medium according to claim 2, wherein said domain control layer and said amorphous soft magnetic layer are alternatively laminated to each other at least twice.
 6. The perpendicular magnetic recording medium according to claim 1, wherein said antiferromagnetic layer is formed of any one of a disordered alloy mainly composed of Mn and Ir and a disordered alloy mainly composed of Cr, Mn, and Pt.
 7. The perpendicular magnetic recording medium according to claim 1, wherein said crystalline soft magnetic layer is formed of any one of an fcc alloy mainly composed of Ni and Fe and an fcc alloy mainly composed of Co.
 8. A perpendicular magnetic recording medium, comprising: a domain control layer formed on a substrate; an amorphous soft magnetic underlayer formed on said domain control layer; a nonmagnetic intermediate layer formed on said amorphous soft magnetic underlayer; and a perpendicular recording layer formed on said nonmagnetic intermediate layer, wherein said domain control layer includes a triple-layer film composed of a first polycrystalline soft magnetic layer, a disordered antiferromagnetic layer, and a second polycrystalline soft magnetic layer, which are laminated to each other from a substrate side.
 9. The perpendicular magnetic recording medium according to claim 1, wherein said substrate has a disk shape, and each of said crystalline soft magnetic layer and said amorphous soft magnetic layer has an unidirectional anisotropy having an easy direction of magnetization in a radial direction of the disk-shaped substrate. 